U.S. patent number 6,053,172 [Application Number 09/083,526] was granted by the patent office on 2000-04-25 for systems and methods for electrosurgical sinus surgery.
This patent grant is currently assigned to ArthroCare Corporation. Invention is credited to Philip E. Eggers, Maria B. Ellsberry, David C. Hovda, Hira V. Thapliyal.
United States Patent |
6,053,172 |
Hovda , et al. |
April 25, 2000 |
Systems and methods for electrosurgical sinus surgery
Abstract
The present invention provides systems and methods for
selectively applying electrical energy to a target location within
the head and neck of a patient's body, particularly including
tissue in the ear, nose and throat. The present invention applies
high frequency (RF) electrical energy to one or more electrode
terminals in the presence of electrically conductive fluid to
remove and/or modify the structure of tissue structures. The
present invention is particularly useful for removing occlusive
media within the small body passages connected to sinus cavities
within the patient's nose to treat chronic sinusitis.
Inventors: |
Hovda; David C. (Mountain View,
CA), Ellsberry; Maria B. (Fremont, CA), Eggers; Philip
E. (Dublin, OH), Thapliyal; Hira V. (Los Altos, CA) |
Assignee: |
ArthroCare Corporation
(Sunnyvale, CA)
|
Family
ID: |
27374556 |
Appl.
No.: |
09/083,526 |
Filed: |
May 22, 1998 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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990374 |
Dec 15, 1997 |
|
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485219 |
Jun 7, 1995 |
5697281 |
|
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Current U.S.
Class: |
128/898; 606/41;
607/104 |
Current CPC
Class: |
A61B
18/148 (20130101); A61B 18/1492 (20130101); A61B
18/1482 (20130101); A61B 18/149 (20130101); A61B
18/1402 (20130101); A61B 18/1485 (20130101); A61B
2018/00601 (20130101); A61B 2018/00392 (20130101); A61B
2018/00029 (20130101); A61B 2018/00982 (20130101); A61B
2018/126 (20130101); A61B 2018/00119 (20130101); A61B
2018/00577 (20130101); A61B 2018/1467 (20130101); A61B
2018/1472 (20130101); A61B 2017/00026 (20130101); A61B
2018/00726 (20130101); A61B 2018/00875 (20130101); A61B
2018/00327 (20130101); A61B 2018/00791 (20130101); A61B
2018/162 (20130101); A61F 2/2493 (20130101); A61B
2018/00702 (20130101); A61B 2017/00247 (20130101); A61B
2018/00678 (20130101); A61B 2017/00084 (20130101); A61B
2018/00583 (20130101); A61B 2018/00827 (20130101); A61B
2018/00083 (20130101); A61B 2018/1253 (20130101); A61B
2018/00178 (20130101); A61B 2018/1273 (20130101); A61B
2018/165 (20130101); A61B 2218/007 (20130101); A61B
18/1206 (20130101); A61B 2018/0016 (20130101); A61B
2218/002 (20130101); A61B 2018/124 (20130101); A61B
18/042 (20130101); A61B 2018/1407 (20130101); A61B
2017/00101 (20130101); A61B 2018/00505 (20130101); A61B
2018/1213 (20130101) |
Current International
Class: |
A61B
18/14 (20060101); A61B 17/00 (20060101); A61B
18/00 (20060101); A61M 1/00 (20060101); A61M
3/02 (20060101); A61M 3/00 (20060101); A61F
2/02 (20060101); A61B 017/39 () |
Field of
Search: |
;128/898
;606/41,42,45-52 ;607/100-105 |
References Cited
[Referenced By]
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WO |
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99/08613 |
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WO |
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1986..
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Primary Examiner: Peffley; Michael
Attorney, Agent or Firm: Raffle; John T.
Parent Case Text
RELATED APPLICATIONS
The present invention is a continuation-in-part of U.S. patent
application No. 08/990,374, filed Dec. 15, 1997, which is a
continuation-in-part of Ser. No. 08/990,374, now U.S. Pat. No.
5,697,281, the complete disclosures of which are incorporated
herein by reference, for all purposes.
The present invention is related to commonly assigned co-pending
U.S. patent application Ser. No. 09/058,571, filed on Apr. 10, 1998
and U.S. patent application Ser. No. 09/054,323, filed on Apr. 2,
1998, U.S. patent application Ser. No. 09/010,382, filed Jan. 21,
1998, and U.S. patent application Ser. No. 09/032,375, filed Feb.
27, 1998, U.S. patent application Ser. No. 08/977,845, filed on
Nov. 25, 1997, Ser. No. 08/942,580, filed on Oct. 2, 1997 Ser. No.
09/026,851, filed Feb. 20, 1998, U.S. application Ser. No.
08/753,227, filed on Nov. 22, 1996, now U.S. Pat. No. 5,873,855,
U.S. application Ser. No. 08/687792, filed on Jul. 18, 1996, now
U.S. Pat. No. 5,843,019, and PCT International Application, U.S.
National Phase Serial No. PCT/US94/05168, filed on May 10, 1994,
now U.S. Pat. No. 5,697,909, which was a continuation-in-part of
U.S. patent application Ser. No. 08/059,681, filed on May 10, 1993
now abandoned which was a continuation-in-part of U.S. patent
application Ser. No. 07/958,977, filed on Oct. 9, 1992, now U.S.
Pat. No. 5,366,443 which was a continuation-in-part of U.S. patent
application Ser. No. 07/817,575, filed on Jan. 7, 1992, abandoned
the complete disclosures of which are incorporated herein by
reference for all purposes. The present invention is also related
to commonly assigned U.S. Pat. No. 5,683,366, filed Nov. 22, 1995,
the complete disclosure of which is incorporated herein by
reference for all purposes.
Claims
What is claimed is:
1. A method for treating tissue in a body lumen within a patient's
nose comprising:
introducing an electrode terminal through an opening in the
patient's head into the nasal cavity;
advancing the electrode terminal into a body lumen coupled to a
sinus cavity;
applying sufficient high frequency voltage to the electrode
terminal to remove at least a portion of the occlusive media within
the body lumen and to convert solid occlusive media molecules into
non-condensable gases; and
aspirating the non-condensable gases from the body lumen.
2. The method of claim 1 further comprising applying sufficient
high frequency voltage to the electrode terminal to effect
molecular dissociation of at least a portion of the occlusive
media.
3. The method of claim 1 wherein the applying step includes
generating a voltage gradient between the electrode terminal and
the tissue, the voltage gradient being sufficient to create an
electric field that breaks down the tissue through molecular
dissociation.
4. The method of claim 1 wherein the positioning step comprises
advancing catheter shaft through the body lumen, the electrode
terminal being located on the distal end portion of the catheter
shaft.
5. The method of claim 1 wherein the high frequency voltage is
sufficient to effect hemostasis of severed blood vessels within the
tissue during the removal step.
6. The method of claim 1 further comprising locating conductive
fluid within the body lumen such that the electrode terminal is
substantially surrounded by the electrically conductive fluid and
electrically conductive fluid is located between the electrode
terminal and the occlusive media.
7. The method of claim 6 further comprising applying high frequency
voltage between the electrode terminal and a return electrode and
generating a current flow path between the return electrode and the
electrode terminal with the electrically conductive fluid.
8. The method of claim 6 further comprising applying sufficient
voltage to the electrode terminal in the presence of the
electrically conducting fluid to vaporize at least a portion of the
fluid between the electrode terminal and the tissue at the target
site.
9. The method of claim 8 further comprising accelerating charged
particles from the vaporized fluid to the tissue to cause
dissociation of the molecular bonds within the tissue
structures.
10. The method of claim 1 wherein the electrode terminal comprises
a single, active electrode at the distal end of a shaft.
11. The method of claim 1 wherein the electrode terminal comprises
a plurality of electrically isolated electrode terminals at the
distal end of a shaft.
12. The method of claim 11 further comprising independently
controlling current flow from at least two of the electrode
terminals based on impedance between the electrode terminal and a
return electrode.
13. The method of claim 1 further comprising aspirating fluid from
the target site during the removal step.
14. The method of claim 1 further comprising axially translating
the electrode terminal through the vacated occlusive media to clear
an opening within the body lumen.
15. A method for treating tissue in a body lumen within a patient's
nose comprising:
introducing an electrode terminal through an opening in the
patient's head into the nasal cavity;
advancing the electrode terminal into a body lumen coupled to a
sinus cavity;
applying sufficient high frequency voltage to the electrode
terminal to remove at least a portion of the occlusive media within
the body lumen; and
aspirating fluid from the target site.
16. The method of claim 15 further comprising applying sufficient
high frequency voltage to the electrode terminal to effect
molecular dissociation of at least a portion of the occlusive
media.
17. The method of claim 15 further comprising applying sufficient
high frequency voltage to the electrode terminal to convert solid
occlusive media molecules into non-condensable gases.
18. The method of claim 17 further comprising aspirating the
non-condensable gases from the body lumen.
19. The method of claim 15 wherein the applying step includes
generating a voltage gradient between the electrode terminal and
the tissue, the voltage gradient being sufficient to create an
electric field that breaks down the tissue through molecular
dissociation.
20. The method of claim 15 wherein the positioning step comprises
advancing catheter shaft through the body lumen, the electrode
terminal being located on the distal end portion of the catheter
shaft.
21. The method of claim 15 wherein the high frequency voltage is
sufficient to effect hemostasis of severed blood vessels within the
tissue during the removal step.
22. The method of claim 15 further comprising locating conductive
fluid within the body lumen such that the electrode terminal is
substantially surrounded by the electrically conductive fluid and
electrically conductive fluid is located between the electrode
terminal and the occlusive media.
23. The method of claim 22 further comprising applying high
frequency voltage between the electrode terminal and a return
electrode and generating a current flow path between the return
electrode and the electrode terminal with the electrically
conductive fluid.
24. The method of claim 22 further comprising applying sufficient
voltage to the electrode terminal in the presence of the
electrically conducting fluid to vaporize at least a portion of the
fluid between the electrode terminal and the tissue at the target
site.
25. The method of claim 15 wherein the electrode terminal comprises
a single, active electrode at the distal end of a shaft.
26. The method of claim 15 wherein the electrode terminal comprises
a plurality of electrically isolated electrode terminals at the
distal end of a shaft.
27. The method of claim 26 further comprising independently
controlling current flow from at least two of the electrode
terminals based on impedance between the electrode terminal and a
return electrode.
28. The method of claim 15 further comprising aspirating fluid from
the target site during the removal step.
29. The method of claim 15 further comprising accelerating charged
particles from the vaporized fluid to the tissue to cause
dissociation of the molecular bonds within the tissue
structures.
30. The method of claim 15 further comprising axially translating
the electrode terminal through the vacated occlusive media to clear
an opening within the body lumen.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to the field of
electrosurgery, and more particularly to surgical devices and
methods which employ high frequency electrical energy to treat
tissue in regions of the head and neck, such as the ear, nose and
throat. The present invention is particularly suited for sinus
surgery and the treatment of sinusitis, rhinitis, nasal polyps and
the like.
Sinuses are the air-filled cavities insides the facial bones that
open into the nasal cavities. Each sinus is lined with a mucous
membrane containing tiny hairs (cilia) that sweep mucus, dust
particles, bacteria and other air pollutants out of the sinuses and
through the natural openings into the back of the nose. This mucus
flow, commonly call "postnasal drip", is a normal bodily function
that prevents the accumulation of dangerous bacteria. Sinusitis is
the inflammation of the mucous membranes of one or more of the
paranasal sinus cavities. Sinusitis is often associated with a
viral or bacterial upper respiratory infection that spreads to the
sinuses. When the sinus opening becomes blocked, the cavities fill,
producing deep pain and pressure. Postnasal or nasal drainage,
nasal congestion with pressure, headaches, sinus infections and
nasal polyps are most commonly associated with chronic
sinusitis.
Treatment of mild sinusitis typically involves antibiotics,
decongestants and analgesics, and is designed to prevent further
complications. For more severe or chronic sinusitis, surgery is
often necessary to return the nose and sinuses to normal function,
particularly with patients who have undergone years of allergy
treatment and still suffer from sinus blockage, or patients born
with small sinuses and nasal passages. Recent developments in the
field of endoscopic surgical techniques and medical devices have
provided skilled physicians with instrumentation and methods to
perform complicated paranasal sinus surgical procedures. Improved
visualization of the nasal cavity and the paranasal sinuses, for
example, has now made these anatomical areas more accessible to the
endoscopic surgeon. As a result, functional endoscopic sinus
surgery (FESS) has become the technique of choice in the surgical
approach to sinus disease.
Another nasal symptom, runny noses (e.g., allergic rhinitis or
vasomotor rhinitis), is typically caused by small shelf-like
structures in the nose called turbinates. Turbinates are
responsible for warming and humidifying the air passing through the
nose into the lungs. When the air contains an irritant, the
turbinates react to the airborne particles by swelling and pouring
mucus, as if the body were trying to block and cleanse the
breathing passage. For temporary relief of swollen turbinates,
decongestant nasal sprays and pills are often prescribed. These
measures, however, have limited effectiveness, and the long term
use of such nasal sprays typically makes the problem worse.
Moreover, decongestant pills may cause high blood pressure,
increase the heart rate and, for some people, cause
sleeplessness.
In the past several years, powered instrumentation, such as
microdebrider devices and lasers, has been used to remove polyps or
other swollen tissue in functional endoscopic sinus surgery.
Microdebriders are disposable motorized cutters having a rotating
shaft with a serrated distal tip for cutting and resecting tissue.
The handle of the microdebrider is typically hollow, and it
accommodates a small vacuum, which serves to aspirate debris. In
this procedure, the distal tip of the shaft is endoscopically
delivered through a nasal passage into the sinus cavity of a
patient, and an endoscope is similarly delivered through the same
or the opposite nasal passage to view the surgical site. An
external motor rotates the shaft and the serrated tip, allowing the
tip to cut the polyps or other tissue responsible for the sinus
blockage. Once the critical blockage is cleared, aeration and
drainage are reestablished and the sinuses heal and return to their
normal function.
While microdebriders have been promising, these devices suffer from
a number of disadvantages. For one thing, the tissue in the nasal
and sinus cavities is extremely vascular, and the microdebrider
severs blood vessels within this tissue, usually causing profuse
bleeding that obstructs the surgeon's view of the target site.
Controlling this bleeding can be difficult since the vacuuming
action tends to promote hemorrhaging from blood vessels disrupted
during the procedure. In addition, the microdebrider often must be
removed from the nose periodically to cauterize severed blood
vessels, which lengthens the procedure. Moreover, the serrated
edges and other fine crevices of the microdebrider can easily
become clogged with debris, which requires the surgeon to remove
and clean the microdebrider during the surgery, further increasing
the length of the procedure. More serious concerns, however, are
that the microdebrider is not precise, and it is often difficult,
during the procedure, to differentiate between the target sinus
tissue, and other structures within the nose, such as cartilage,
bone or cranial. Thus, the surgeon must be extremely careful to
minimize damage to the cartilage and bone within the nose, and to
avoid damaging nerves, such as the optic nerve.
Lasers were initially considered ideal for sinus surgery because
lasers ablate or vaporize tissue with heat, which also acts to
cauterize and seal the small blood vessels in the tissue.
Unfortunately, lasers are both expensive and somewhat tedious to
use in these procedures. Another disadvantage with lasers is the
difficulty in judging the depth of tissue ablation. Since the
surgeon generally points and shoots the laser without contacting
the tissue, he or she does not receive any tactile feedback to
judge how deeply the laser is cutting. Because healthy tissue,
cartilage, bone and/or cranial nerves often lie within close
proximity of the sinus tissue, it is essential to maintain a
minimum depth of tissue damage, which cannot always be ensured with
a laser.
Sleep-apnea syndrome is a medical condition characterized by
daytime hypersomnolence, intellectual deterioration, cardiac
arrhythmias, snoring and thrashing during sleep. This syndrome is
classically divided into two types. One type, termed "central sleep
apnea syndrome", is characterized by repeated loss of respiratory
effort.
The second type, termed obstructive sleep apnea syndrome, is
characterized by repeated apneic episodes during sleep resulting
from obstruction of the patient's upper airway or that portion of
the patient's respiratory tract which is cephalad to, and does not
include, the larynx.
Treatment for sleep apnea has included various medical, surgical
and physical measures. Medical measures include the use of
medications and the avoidance of central nervous system
depressants, such as sedatives or alcohol. These measures are
sometimes helpful, but rarely completely effective. Surgical
interventions have included uvuolopalatopharyngoplasty,
tonsillectomy, surgery to correct severe retrognathia and
tracheostomy. While these procedures are effective, the risk of
surgery in these patients is often prohibitive, and the procedures
are unacceptable to the patient. Physical measures have included
weight loss, nasopharygeal airways, nasal CPAP and various tongue
retaining devices used nocturnally. These measures are cumbersome,
uncomfortable and difficult to use for prolonged periods of
time.
Recently, RF energy has been used to selectively ablate portions of
the tongue to treat air passage disorders, such as sleep apnea.
This procedure, which was developed by Somnus Medical Technologies
of Sunnyvale, Calif., involves the use of a monopolar electrode
that directs RF current into the target tissue to desiccate or
destroy tissue in the tongue. Of course, such monopolar devices
suffer from the disadvantage that the electric current will flow
through undefined paths in the patient's body, thereby increasing
the risk of unwanted electrical stimulation to portions of the
patient's body. In addition, since the defined path through the
patient's body has a relatively high impedance (because of the
large distance or resistivity of the patient's body), large voltage
differences must typically be applied between the return and active
electrodes in order to generate a current suitable for ablation or
cutting of the target tissue. This current, however, may
inadvertently flows along body paths having less impedance than the
defined electrical path, which will substantially increase the
current flowing through these paths, possibly causing damage to or
destroying surrounding tissue or neighboring peripheral nerves.
SUMMARY OF THE INVENTION
The present invention provides systems, apparatus and methods for
selectively applying electrical energy to structures in the head
and neck of a patient's body, such as tissue within the ear, nose
and throat. The systems and methods of the present invention are
particularly useful for ablation and hemostasis of tissue in sinus
surgery (e.g., chronic sinusitis and/or removal of polypectomies)
and for removing occlusive media within small body passages within
and around the nasal cavity.
In one aspect of the invention, a method is provided for removing
occlusive media in one of the small body passages coupled to the
nasal cavity or a paranasal sinus of a patient to remove a
blockage, such as swollen nasal tissue, mucus membranes, polyps,
neoplasms, or the like. In this method, one or more electrode
terminal(s) are delivered into the nasal cavity, either
endoscopically through one of the nasal passages or directly in an
open procedure. An electrically conductive fluid, such as isotonic
saline, is delivered to the target site within or around the nasal
cavity to substantially surround the electrode terminal(s) with the
fluid. The fluid may be delivered through an instrument to the
specific target site, or the entire nasal cavity may be filled with
conductive fluid such that the electrode terminal(s) are submerged
during the procedure. In both embodiments, high frequency voltage
is applied between the electrode terminal(s) and one or more return
electrode(s) to volumetrically remove or ablate at least a portion
of the occlusive media within the body passage.
In a specific configuration, the occlusive media or nasal tissue is
removed by molecular dissociation or disintegration processes. In
these embodiments, the high frequency voltage applied to the
electrode terminal(s) is sufficient to vaporize an electrically
conductive fluid (e.g., gel or saline) between the electrode
terminal(s) and the tissue. Within the vaporized fluid, a ionized
plasma is formed and charged particles (e.g., electrons) are
accelerated towards the tissue to cause the molecular breakdown or
disintegration of several cell layers of the tissue. This molecular
dissociation is accompanied by the volumetric removal of the
tissue. The short range of the accelerated charged particles within
the plasma layer confines the molecular dissociation process to the
surface layer to minimize damage and necrosis to the underlying
tissue. This process can be precisely controlled to effect the
volumetric removal of tissue as thin as 10 to 150 microns with
minimal heating of, or damage to, surrounding or underlying tissue
structures. A more complete description of this phenomena is
described in commonly assigned U.S. Pat. No. 5,683,366, the
complete disclosure of which is incorporated herein by
reference.
The present invention offers a number of advantages over current
microdebrider and laser techniques for endoscopic sinus surgery.
The ability to precisely control the volumetric removal of tissue
results in a field of tissue ablation or removal that is very
defined, consistent and predictable. The shallow depth of tissue
heating also helps to minimize or completely eliminate damage to
healthy tissue structures, cartilage, bone and/or cranial nerves
that are often adjacent the target sinus tissue. In addition, small
blood vessels within the nose are simultaneously cauterized and
sealed as the tissue is removed to continuously maintain hemostasis
during the procedure. This increases the surgeon's field of view,
and shortens the length of the procedure. Moreover, since the
present invention allows for the use of electrically conductive
fluid (contrary to prior art bipolar and monopolar electrosurgery
techniques), isotonic saline may be used during the procedure.
Saline is the preferred medium for irrigation because it has the
same concentration as the body's fluids and, therefore, is not
absorbed into the body as much as other fluids.
Apparatus according to the present invention generally include an
electrosurgical catheter having a shaft with proximal and distal
ends, one or more electrode terminal(s) at the distal end and one
or more connectors coupling the electrode terminal(s) to a source
of high frequency electrical energy. The catheter shaft will have
at least a distal end portion sized for delivery through the small
body lumens coupled to the nasal cavity and/or the sinus cavities.
Depending on the patient's body structure, the distal end portion
of the shaft will usually have a diameter of less than 3 mm,
preferably less than 0.5 mm. The shaft may additionally include a
lens at the distal end coupled to a proximal eye piece for
endoscopically viewing the target tissue. Alternatively, the
endoscope may be a separate instrument that is introduced through
the same or a different opening as the electrosurgical
catheter.
The apparatus will preferably further include a fluid delivery
element for delivering electrically conducting fluid to the
electrode terminal(s) and the target site. The fluid delivery
element may be located on the catheter, e.g., a fluid lumen or
tube, or it may be part of a separate instrument. Alternatively, an
electrically conducting gel or spray, such as a saline electrolyte
or other conductive gel, may be applied the target site. In this
embodiment, the apparatus may not have a fluid delivery element. In
both embodiments, the electrically conducting fluid will preferably
generate a current flow path between the electrode terminal(s) and
one or more return electrode(s). In an exemplary embodiment, the
return electrode is located on the catheter and spaced a sufficient
distance from the electrode terminal(s) to substantially avoid or
minimize current shorting therebetween and to shield the return
electrode from tissue at the target site.
In a specific configuration, the electrosurgical catheter will
include an electrically insulating electrode support member having
a tissue treatment surface at the distal end of the probe. One or
more electrode terminal(s) are coupled to, or integral with, the
electrode support member such that the electrode terminal(s) are
spaced from the return electrode. In one embodiment, the catheter
includes an electrode array having a plurality of electrically
isolated electrode terminals embedded into the electrode support
member such that the electrode terminals extend about 0.2 mm to
about 10 mm distally from the tissue treatment surface of the
electrode support member. In this embodiment, the catheter will
further include one or more lumens for delivering electrically
conductive fluid to one or more openings around the tissue
treatment surface of the electrode support member. In an exemplary
embodiment, the lumen will extend through a fluid tube exterior to
the catheter shaft that ends proximal to the return electrode.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of an electrosurgical system
incorporating a power supply and in electrosurgical probe for
tissue ablation, resection, incision, contraction and for vessel
hemostasis according to the present invention;
FIG. 2 is a side view of an electrosurgical probe according to the
present invention;
FIG. 3 is an end view of the probe of FIG. 2;
FIG. 4 is a cross sectional view of the electrosurgical probe of
FIG. 1;
FIG. 5 is an exploded view of a proximal portion of the
electrosurgical probe;
FIGS. 6A and 6B are perspective and end views, respectively, of an
alternative electrosurgical probe incorporating an inner fluid
lumen;
FIGS. 7A-7C are cross-sectional views of the distal portions of
three different embodiments of an electrosurgical probe according
to the present invention;
FIGS. 8A and 8B are cross-sectional and end views, respectively, of
yet another electrosurgical probe incorporating flattened electrode
terminals;
FIG. 9 illustrates an electrosurgical probe with a 90.degree.
distal bend and a lateral fluid lumen;
FIG. 10 illustrates an electrosurgical system with a separate fluid
delivery instrument according to the present invention;
FIG. 11 illustrates an endoscopic sinus surgery procedure, wherein
an endoscope is delivered through a nasal passage to view a
surgical site within the nasal cavity of the patient;
FIG. 12 illustrates an endoscopic sinus surgery procedure with one
of the probes described above according to the present
invention;
FIGS. 13A and 13B illustrate a detailed view of the sinus surgery
procedure, illustrating ablation of tissue according to the present
invention;
FIG. 14 illustrates a procedure for treating obstructive sleep
disorders, such as sleep apnea, according to the present
invention;
FIG. 15 illustrates a catheter system for electrosurgical treatment
of body structures within the head and neck according to the
present invention; FIG. 16 is a cross-section view of a working end
of a catheter according to one embodiment of the present
invention;
FIG. 17A is a cross-section view of a working end of a catheter
according to a second embodiment of the present invention;
FIG. 17B is an end view of the catheter of FIG. 17A;
FIG. 18 is a sagittal section of a patient's head illustrating a
method of removing tissue from body lumens within a patient's nose
according to the present invention; and
FIG. 19 is a coronal section of a patient's head illustrating the
paranasal sinuses.
DESCRIPTION OF SPECIFIC EMBODIMENTS
The present invention provides systems and methods for selectively
applying electrical energy to a target location within or on a
patient's body, particularly including tissue in head and neck,
such as the ear, mouth, pharynx, larynx, esophagus, nasal cavity
and sinuses. These procedures may be performed through the mouth or
nose using speculae or gags, or using endoscopic techniques, such
as functional endoscopic sinus surgery (FESS). These procedures may
include the removal of swollen tissue, chronically-diseased
inflamed and hypertrophic mucus linings, polyps and/or neoplasms
from the various anatomical sinuses of the skull, the turbinates
and nasal passages, in the tonsil, adenoid, epi-glottic and
supra-glottic regions, and salivary glands, submucus resection of
the nasal septum, excision of diseased tissue and the like. In
other procedures, the present invention may be useful for collagen
shrinkage, ablation and/or hemostasis in procedures for treating
snoring and obstructive sleep apnea (e.g., soft palate, such as the
uvula, or tongue/pharynx stiffening, and midline glossectomies),
for gross tissue removal, such as tonsillectomies, adenoidectomies,
tracheal stenosis and vocal cord polyps and lesions, or for the
resection or ablation of facial tumors or tumors within the mouth
and pharynx, such as glossectomies, laryngectomies, acoustic
neuroma procedures and nasal ablation procedures. In addition, the
present invention is useful for procedures within the ear, such as
stapedotomies, tympanostomies or the like.
The present invention may also be useful for cosmetic and plastic
surgery procedures in the head and neck. For example, the present
invention is particularly useful for ablation and sculpting of
cartilage tissue, such as the cartilage within the nose that is
sculpted during rhinoplasty procedures. The present invention may
also be employed for skin tissue removal and/or collagen shrinkage
in the epidermis or dermis tissue in the head and neck, e.g., the
removal of pigmentations, vascular lesions (e.g., leg veins),
scars, tattoos, etc., and for other surgical procedures on the
skin, such as tissue rejuvenation, cosmetic eye procedures
(blepharoplasties), wrinkle removal, tightening muscles for
facelifts or browlifts, hair removal and/or transplant procedures,
etc.
For convenience, the remaining disclosure will be directed
specifically to the treatment of sinisitis and related disorders,
but it will be appreciated that the system and method can be
applied equally well to procedures involving other tissues of the
body, as well as to other procedures including open procedures,
intravascular procedures, urology, laparascopy, arthroscopy,
thoracoscopy or other cardiac procedures, cosmetic surgery,
orthopedics, gynecology, otorhinolaryngology, spinal and neurologic
procedures, oncology and the like.
In the present invention, high frequency (RF) electrical energy is
applied to one or more electrode terminals in the presence of
electrically conductive fluid to remove and/or modify the structure
of tissue structures. Depending on the specific procedure, the
present invention may be used to: (1) volumetrically remove tissue
or cartilage (i.e., ablate or effect molecular dissociation of the
tissue structure); (2) cut or resect tissue; (3) shrink or contract
collagen connective tissue; and/or (4) coagulate severed blood
vessels.
In some procedures, e.g., soft palate or tongue/pharynx stiffening,
it is desired to shrink or contract collagen connective tissue at
the target site. In these procedures, the RF energy heats the
tissue directly by virtue of the electrical current flow
therethrough, and/or indirectly through the exposure of the tissue
to fluid heated by RF energy, to elevate the tissue temperature
from normal body temperatures (e.g., 37.degree. C.) to temperatures
in the range of 45.degree. C. to 90.degree. C., preferably in the
range from about 60.degree. C. to 70.degree. C. Thermal shrinkage
of collagen fibers occurs within a small temperature range which,
for mammalian collagen is in the range from 60.degree. C. to
70.degree. C. (Deak, G., et al., "The Thermal Shrinkage Process of
Collagen Fibres as Revealed by Polarization Optical Analysis of
Topooptical Staining Reactions," Acta Morphologica Acad. Sci. of
Hungary, Vol. 15(2), pp 195-208, 1967). Collagen fibers typically
undergo thermal shrinkage in the range of 60.degree. C. to about
70.degree. C. Previously reported research has attributed thermal
shrinkage of collagen to the cleaving of the internal stabilizing
cross-linkages within the collagen matrix (Deak, ibid). It has also
been reported that when the collagen temperature is increased above
70.degree. C., the collagen matrix begins to relax again and the
shrinkage effect is reversed resulting in no net shrinkage (Allain,
J. C., et al., "Isometric Tensions Developed During the
Hydrothermal Swelling of Rat Skin,"0 Connective Tissue Research,
Vol. 7, pp 127-133, 1980). Consequently, the controlled heating of
tissue to a precise depth is critical to the achievement of
therapeutic collagen shrinkage. A more detailed description of
collagen shrinkage can be found in U.S. patent application Ser. No.
08/942,580 filed on Oct. 2, 1997, (Attorney Docket No.
16238-001300).
The preferred depth of heating to effect the shrinkage of collagen
in the heated region (i.e., the depth to which the tissue is
elevated to temperatures between 60.degree. C. to 70.degree. C.)
generally depends on (1) the thickness of the tissue, (2) the
location of nearby structures (e.g., nerves) that should not be
exposed to damaging temperatures, and/or (3) the location of the
collagen tissue layer within which therapeutic shrinkage is to be
effected. The depth of heating is usually in the range from 0 to
3.5 mm. In the case of collagen within the soft palate or uvula,
the depth of heating is preferably in the range from about 0.5 to
about 3.5 mm.
In another method of the present invention, the tissue structures
are volumetrically removed or ablated. In this procedure, a high
frequency voltage difference is applied between one or more
electrode terminal(s) and one or more return electrode(s) to
develop high electric field intensities in the vicinity of the
target tissue site. The high electric field intensities lead to
electric field induced molecular breakdown of target tissue through
molecular dissociation (rather than thermal evaporation or
carbonization). Applicant believes that the tissue structure is
volumetrically removed through molecular disintegration of larger
organic molecules into smaller molecules and/or atoms, such as
hydrogen, oxides of carbon, hydrocarbons and nitrogen compounds.
This molecular disintegration completely removes the tissue
structure, as opposed to dehydrating the tissue material by the
removal of liquid within the cells of the tissue, as is typically
the case with electrosurgical desiccation and vaporization.
The high electric field intensities may be generated by applying a
high frequency voltage that is sufficient to vaporize an
electrically conducting fluid over at least a portion of the
electrode terminal(s) in the region between the distal tip of the
electrode terminal(s) and the target tissue. The electrically
conductive fluid may be a gas or liquid, such as isotonic saline,
delivered to the target site, or a viscous fluid, such as a gel,
that is located at the target site. In the latter embodiment, the
electrode terminal(s) are submersed in the electrically conductive
gel during the surgical procedure. Since the vapor layer or
vaporized region has a relatively high electrical impedance, it
increases the voltage differential between the electrode terminal
tip and the tissue and causes ionization within the vapor layer due
to the presence of an ionizable species (e.g., sodium when isotonic
saline is the electrically conducting fluid). This ionization,
under optimal conditions, induces the discharge of energetic
electrons and photons from the vapor layer and to the surface of
the target tissue. This energy may be in the form of energetic
photons (e.g., ultraviolet radiation), energetic particles (e.g.,
electrons) or a combination thereof. A more detailed description of
this cold ablation phenomena, termed Coblation.TM., can be found in
commonly assigned U.S. Pat. No. 5,683,366 the complete disclosure
of which is incorporated herein by reference.
The present invention applies high frequency (RF) electrical energy
in an electrically conducting fluid environment to remove (i.e.,
resect, cut or ablate) or contract a tissue structure, and to seal
transected vessels within the region of the target tissue. The
present invention is particularly useful for sealing larger
arterial vessels, e.g., on the order of 1 mm or greater. In some
embodiments, a high frequency power supply is provided having an
ablation mode, wherein a first voltage is applied to an electrode
terminal sufficient to effect molecular dissociation or
disintegration of the tissue, and a coagulation mode, wherein a
second, lower voltage is applied to an electrode terminal (either
the same or a different electrode) sufficient to achieve hemostasis
of severed vessels within the tissue. In other embodiments, an
electrosurgical probe is provided having one or more coagulation
electrode(s) configured for sealing a severed vessel, such as an
arterial vessel, and one or more electrode terminals configured for
either contracting the collagen fibers within the tissue or
removing (ablating) the tissue, e.g., by applying sufficient energy
to the tissue to effect molecular dissociation. In the latter
embodiments, the coagulation electrode(s) may be configured such
that a single voltage can be applied to coagulate with the
coagulation electrode(s), and to ablate or contract with the
electrode terminal(s). In other embodiments, the power supply is
combined with the coagulation probe such that the coagulation
electrode is used when the power supply is in the coagulation mode
(low voltage), and the electrode terminal(s) are used when the
power supply is in the ablation mode (higher voltage).
In the method of the present invention, one or more electrode
terminals are brought into close proximity to tissue at a target
site, and the power supply is activated in the ablation mode such
that sufficient voltage is applied between the electrode terminals
and the return electrode to volumetrically remove the tissue
through molecular dissociation, as described below. During this
process, vessels within the tissue will be severed. Smaller vessels
will be automatically sealed with the system and method of the
present invention. Larger vessels, and those with a higher flow
rate, such as arterial vessels, may not be automatically sealed in
the ablation mode. In these cases, the severed vessels may be
sealed by activating a control (e.g., a foot pedal) to reduce the
voltage of the power supply into the coagulation mode. In this
mode, the electrode terminals may be pressed against the severed
vessel to provide sealing and/or coagulation of the vessel.
Alternatively, a coagulation electrode located on the same or a
different probe may be pressed against the severed vessel. Once the
vessel is adequately sealed, the surgeon activates a control (e.g.,
another foot pedal) to increase the voltage of the power supply
back into the ablation mode.
The present invention is particularly useful for removing or
ablating tissue around nerves, such as spinal or cranial nerves,
e.g., the olfactory nerve on either side of the nasal cavity, the
optic nerve within the optic and cranial canals, the palatine nerve
within the nasal cavity, soft palate, uvula and tonsil, etc. One of
the significant drawbacks with the prior art microdebriders and
lasers is that these devices do not differentiate between the
target tissue and the surrounding nerves or bone. Therefore, the
surgeon must be extremely careful during these procedures to avoid
damage to the bone or nerves within and around the nasal cavity. In
the present invention, the Coblation.TM. process for removing
tissue results in extremely small depths of collateral tissue
damage as discussed above.
This allows the surgeon to remove tissue close to a nerve without
causing collateral damage to the nerve fibers.
In addition to the generally precise nature of the novel mechanisms
of the present invention, applicant has discovered an additional
method of ensuring that adjacent nerves are not damaged during
tissue removal. According to the present invention, systems and
methods are provided for distinguishing between the fatty tissue
immediately surrounding nerve fibers and the normal tissue that is
to be removed during the procedure. Nerves usually comprise a
connective tissue sheath, or endoneurium, enclosing the bundles of
nerve fibers to protect these nerve fibers. This protective tissue
sheath typically comprises a fatty tissue (e.g., adipose tissue)
having substantially different electrical properties than the
normal target tissue, such as the turbinates, polyps, mucus tissue
or the like, that are, for example, removed from the nose during
sinus procedures. The system of the present invention measures the
electrical properties of the tissue at the tip of the probe with
one or more electrode terminal(s). These electrical properties may
include electrical conductivity at one, several or a range of
frequencies (e.g., in the range from 1 kHz to 100 MHz), dielectric
constant, capacitance or combinations of these. In this embodiment,
an audible signal may be produced when the sensing electrode(s) at
the tip of the probe detects the fatty tissue surrounding a nerve,
or direct feedback control can be provided to only supply power to
the electrode terminal(s) either individually or to the complete
array of electrodes, if and when the tissue encountered at the tip
or working end of the probe is normal tissue based on the measured
electrical properties.
In one embodiment, the current limiting elements (discussed in
detail above) are configured such that the electrode terminals will
shut down or turn off when the electrical impedance reaches a
threshold level. When this threshold level is set to the impedance
of the fatty tissue surrounding nerves, the electrode terminals
will shut off whenever they come in contact with, or in close
proximity to, nerves. Meanwhile, the other electrode terminals,
which are in contact with or in close proximity to nasal tissue,
will continue to conduct electric current to the return electrode.
This selective ablation or removal of lower impedance tissue in
combination with the Coblation.TM. mechanism of the present
invention allows the surgeon to precisely remove tissue around
nerves or bone.
In addition to the above, applicant has discovered that the
Coblation.TM. mechanism of the present invention can be manipulated
to ablate or remove certain tissue structures, while having little
effect on other tissue structures. As discussed above, the present
invention uses a technique of vaporizing electrically conductive
fluid to form a plasma layer or pocket around the electrode
terminal(s), and then inducing the discharge of energy from this
plasma or vapor layer to break the molecular bonds of the tissue
structure. Based on initial experiments, applicants believe that
the free electrons within the ionized vapor layer are accelerated
in the high electric fields near the electrode tip(s). When the
density of the vapor layer (or within a bubble formed in the
electrically conducting liquid) becomes sufficiently low (i.e.,
less than approximately 10.sub.20 atoms/cm.sup.3 for aqueous
solutions), the electron mean free path increases to enable
subsequently injected electrons to cause impact ionization within
these regions of low density (i.e., vapor layers or bubbles).
Energy evolved by the energetic electrons (e.g., 4 to 5 eV) can
subsequently bombard a molecule and break its bonds, dissociating a
molecule into free radicals, which then combine into final gaseous
or liquid species.
The energy evolved by the energetic electrons may be varied by
adjusting a variety of factors, such as: the number of electrode
terminals; electrode size and spacing;
electrode surface area; asperities and sharp edges on the electrode
surfaces; electrode materials; applied voltage and power; current
limiting means, such as inductors; electrical conductivity of the
fluid in contact with the electrodes; density of the fluid; and
other factors. Accordingly, these factors can be manipulated to
control the energy level of the excited electrons. Since different
tissue structures have different molecular bonds, the present
invention can be configured to break the molecular bonds of certain
tissue, while having too low an energy to break the molecular bonds
of other tissue. For example, fatty tissue, (e.g., adipose) tissue
has double bonds that require a substantially higher energy level
than 4 to 5 eV to break. Accordingly, the present invention in its
current configuration generally does not ablate or remove such
fatty tissue. Of course, factors may be changed such that these
double bonds can be broken (e.g., increasing voltage or changing
the electrode configuration to increase the current density at the
electrode tips).
The electrosurgical instrument will comprise a shaft or a handpiece
having a proximal end and a distal end which supports one or more
electrode terminal(s). The shaft or handpiece may assume a wide
variety of configurations, with the primary purpose being to
mechanically support the active electrode and permit the treating
physician to manipulate the electrode from a proximal end of the
shaft. The shaft may be rigid or flexible, with flexible shafts
optionally being combined with a generally rigid external tube for
mechanical support. Flexible shafts may be combined with pull
wires, shape memory actuators, and other known mechanisms for
effecting selective deflection of the distal end of the shaft to
facilitate positioning of the electrode array. The shaft will
usually include a plurality of wires or other conductive elements
running axially therethrough to permit connection of the electrode
array to a connector at the proximal end of the shaft.
For procedures within the nose, the shaft will have a suitable
diameter and length to allow the surgeon to reach the target site
(e.g., a blockage in the nasal cavity or one of the sinuses) by
delivering the probe shaft through one of the nasal passages or
another opening (e.g., an opening in the eye or through an opening
surgically creating during the procedure). Thus, the shaft will
usually have a length in the range of about 5-25 cm, and a diameter
in the range of about 0.5 to 5 mm. For procedures in the small
passages of the nose, the shaft diameter will usually be less than
3 mm, preferably less than about 0.5 mm. Likewise, for procedures
in the ear, the shaft should have a length in the range of about 3
to 20 cm, and a diameter of about 0.3 to 5 mm. For procedures in
the mouth or upper throat, the shaft will have any suitable length
and diameter that would facilitate handling by the surgeon. For
procedures in the lower throat, such as laryngectomies, the shaft
will be suitably designed to access the larynx. For example, the
shaft may be flexible, or have a distal bend to accommodate the
bend in the patient's throat. In this regard, the shaft may be a
rigid shaft having a specifically designed bend to correspond with
the geometry of the mouth and throat, or it may have a flexible
distal end, or it may be part of a catheter. In any of these
embodiments, the shaft may also be introduced through rigid or
flexible endoscopes. Specific shaft designs will be described in
detail in connection with the figures hereinafter.
The current flow path between the electrode terminal(s) and the
return electrode(s) may be generated by submerging the tissue site
in an electrical conducting fluid (e.g., within a viscous fluid,
such as an electrically conductive gel) or by directing an
electrically conducting fluid along a fluid path to the target site
(i.e., a liquid, such as isotonic saline, or a gas, such as argon).
This latter method is particularly effective in a dry environment
(i.e., the tissue is not submerged in fluid) because the
electrically conducting fluid provides a suitable current flow path
from the electrode terminal to the return electrode. A more
complete description of an exemplary method of directing
electrically conducting fluid between the active and return
electrodes is described U.S. Pat. No. 5,697,281, previously
incorporated herein by reference.
In some procedures, it may also be necessary to retrieve or
aspirate the electrically conductive fluid after it has been
directed to the target site. For example, in procedures in the
nose, mouth or throat, it may be desirable to aspirate the fluid so
that it does not flow down the patient's throat. In addition, it
may be desirable to aspirate small pieces of tissue that are not
completely disintegrated by the high frequency energy, or other
fluids at the target site, such as blood, mucus, the gaseous
products of ablation, etc.
Accordingly, the system of the present invention will usually
include a suction lumen in the probe, or on another instrument, for
aspirating fluids from the target site.
The present invention may use a single active electrode terminal or
an electrode array distributed over a contact surface of a probe.
In the latter embodiment, the electrode array usually includes a
plurality of independently current-limited and/or power-controlled
electrode terminals to apply electrical energy selectively to the
target tissue while limiting the unwanted application of electrical
energy to the surrounding tissue and environment resulting from
power dissipation into surrounding electrically conductive liquids,
such as blood, normal saline, electrically conductive gel and the
like. The electrode terminals may be independently current-limited
by isolating the terminals from each other and connecting each
terminal to a separate power source that is isolated from the other
electrode terminals. Alternatively, the electrode terminals may be
connected to each other at either the proximal or distal ends of
the instrument to form a single wire that couples to a power
source.
In one configuration, each individual electrode terminal in the
electrode array is electrically insulated from all other electrode
terminals in the array within said instrument and is connected to a
power source which is isolated from each of the other electrode
terminals in the array or to circuitry which limits or interrupts
current flow to the electrode terminal when low resistivity
material (e.g., blood, electrically conductive saline irrigant or
electrically conductive gel) causes a lower impedance path between
the return electrode and the individual electrode terminal. The
isolated power sources for each individual electrode terminal may
be separate power supply circuits having internal impedance
characteristics which limit power to the associated electrode
terminal when a low impedance return path is encountered. By way of
example, the isolated power source may be a user selectable
constant current source. In this embodiment, lower impedance paths
will automatically result in lower resistive heating levels since
the heating is proportional to the square of the operating current
times the impedance. Alternatively, a single power source may be
connected to each of the electrode terminals through independently
actuatable switches, or by independent current limiting elements,
such as inductors, capacitors, resistors and/or combinations
thereof. The current limiting elements may be provided in the
instrument, connectors, cable, controller or along the conductive
path from the controller to the distal tip of the instrument.
Alternatively, the resistance and/or capacitanct may occur on the
surface of the active electrode terminal(s) due to oxide layers
which form selected electrode terminals (e.g., titanium or a
resistive coating on the surface of metal, such as platinum).
The tip region of the instrument may comprise many independent
electrode terminals designed to deliver electrical energy in the
vicinity of the tip. The selective application of electrical energy
to the conductive fluid is achieved by connecting each individual
electrode terminal and the return electrode to a power source
having independently controlled or current limited channels. The
return electrode(s) may comprise a single tubular member of
conductive material proximal to the electrode array at the tip
which also serves as a conduit for the supply of the electrically
conducting fluid between the active and return electrodes.
Alternatively, the instrument may comprise an array of return
electrodes at the distal tip of the instrument (together with the
active electrodes) to maintain the electric current at the tip. The
application of high frequency voltage between the return
electrode(s) and the electrode array results in the generation of
high electric field intensities at the distal tips of the electrode
terminals with conduction of high frequency current from each
individual electrode terminal to the return electrode. The current
flow from each individual electrode terminal to the return
electrode(s) is controlled by either active or passive means, or a
combination thereof, to deliver electrical energy to the
surrounding conductive fluid while minimizing energy delivery to
surrounding (non-target) tissue.
The application of a high frequency voltage between the return
electrode(s) and the electrode terminal(s) for appropriate time
intervals effects cutting, removing, ablating, shaping, contracting
or otherwise modifying the target tissue. The tissue volume over
which energy is dissipated (i.e., a high current density exists)
may be precisely controlled, for example, by the use of a
multiplicity of small electrode terminals whose effective diameters
or principal dimensions range from about 5 mm to 0.01 mm,
preferably from about 2 mm to 0.05 mm, and more preferably from
about 1 mm to 0.1 mm. Electrode areas for both circular and
non-circular terminals will have a contact area (per electrode
terminal) below 25 mm.sup.2, preferably being in the range from
0.0001 mm.sup.2 to 1 mm.sup.2, and more preferably from 0.005
mm.sup.2 to 0.5 mm.sup.2. The circumscribed area of the electrode
array is in the range from 0.25 mm.sup.2 to 75 mm.sup.2, preferably
from 0.5 mm.sup.2 to 40 mm.sup.2, and will usually include at least
two isolated electrode terminals, preferably at least five
electrode terminals, often greater than 10 electrode terminals and
even 50 or more electrode terminals, disposed over the distal
contact surfaces on the shaft. The use of small diameter electrode
terminals increases the electric field intensity and reduces the
extent or depth of tissue heating as a consequence of the
divergence of current flux lines which emanate from the exposed
surface of each electrode terminal.
The area of the tissue treatment surface can vary widely, and the
tissue treatment surface can assume a variety of geometries, with
particular areas and geometries being selected for specific
applications. Active electrode surfaces can have areas in the range
from 0.25 mm.sup.2 to 75 mm.sup.2, usually being from about 0.5
mm.sup.2 to 40 mm.sup.2. The geometries can be planar, concave,
convex, hemispherical, conical, linear "in-line" array or virtually
any other regular or irregular shape. Most commonly, the active
electrode(s) or electrode terminal(s) will be formed at the distal
tip of the electrosurgical instrument shaft, frequently being
planar, disk-shaped, or hemispherical surfaces for use in reshaping
procedures or being linear arrays for use in cutting. Alternatively
or additionally, the active electrode(s) may be formed on lateral
surfaces of the electrosurgical instrument shaft (e.g., in the
manner of a spatula), facilitating access to certain body
structures in endoscopic procedures.
In the representative embodiments, the electrode terminals comprise
substantially rigid wires protruding outward from the tissue
treatment surface of the electrode support member. Usually, the
wires will extend about 0.1 to 4.0 mm, preferably about 0.2 to 1
mm, from the distal surface of the support member. In the exemplary
embodiments, the electrosurgical instrument includes between about
two to fifty electrically isolated electrode terminals, and
preferably between about three to twenty electrode terminals.
The electrically conducting fluid should have a threshold
conductivity to provide a suitable conductive path between the
return electrode(s) and the electrode terminal(s). The electrical
conductivity of the fluid (in units of milliSiemans per centimeter
or mS/cm) will usually be greater than 0.2 mS/cm, preferably will
be greater than 2 mS/cm and more preferably greater than 10 mS/cm.
In an exemplary embodiment, the electrically conductive fluid is
isotonic saline, which has a conductivity of about 17 mS/cm.
In some embodiments, the electrode support and the fluid outlet may
be recessed from an outer surface of the instrument or handpiece to
confine the electrically conductive fluid to the region immediately
surrounding the electrode support. In addition, the shaft may be
shaped so as to form a cavity around the electrode support and the
fluid outlet. This helps to assure that the electrically conductive
fluid will remain in contact with the electrode terminal(s) and the
return electrode(s) to maintain the conductive path therebetween.
In addition, this will help to maintain a vapor or plasma layer
between the electrode terminal(s) and the tissue at the treatment
site throughout the procedure, which reduces the thermal damage
that might otherwise occur if the vapor layer were extinguished due
to a lack of conductive fluid. Provision of the electrically
conductive fluid around the target site also helps to maintain the
tissue temperature at desired levels.
The voltage applied between the return electrode(s) and the
electrode array will be at high or radio frequency, typically
between about 5 kHz and 20 MHz, usually being between about 30 kHz
and 2.5 MHz, preferably being between about 50 kHz and 500 kHz,
more preferably less than 350 kHz, and most preferably between
about 100 kHz and 200 kHz. The RMS (root mean square) voltage
applied will usually be in the range from about 5 volts to 1000
volts, preferably being in the range from about 10 volts to 500
volts depending on the electrode terminal size, the operating
frequency and the operation mode of the particular procedure or
desired effect on the tissue (i.e., contraction, coagulation or
ablation). Typically, the peak-to-peak voltage will be in the range
of 10 to 2000 volts, preferably in the range of 20 to 1200 volts
and more preferably in the range of about 40 to 800 volts (again,
depending on the electrode size, the operating frequency and the
operation mode).
As discussed above, the voltage is usually delivered in a series of
voltage pulses or alternating current of time varying voltage
amplitude with a sufficiently high frequency (e.g., on the order of
5 kHz to 20 MHz) such that the voltage is effectively applied
continuously (as compared with e.g., lasers claiming small depths
of necrosis, which are generally pulsed about 10 to 20 Hz). In
addition, the duty cycle (i.e., cumulative time in any one-second
interval that energy is applied) is on the order of about 50% for
the present invention, as compared with pulsed lasers which
typically have a duty cycle of about 0.0001%.
The preferred power source of the present invention delivers a high
frequency current selectable to generate average power levels
ranging from several milliwatts to tens of watts per electrode,
depending on the volume of target tissue being heated, and/or the
maximum allowed temperature selected for the instrument tip. The
power source allows the user to select the voltage level according
to the specific requirements of a particular FESS procedure,
arthroscopic surgery, dermatological procedure, ophthalmic
procedures, open surgery or other endoscopic surgery procedure. A
description of a suitable power source can be found in U.S.
Provisional Patent Application No. 60/062,997, filed on Oct. 23,
1997 (Attorney Docket No. 16238-007400), the complete disclosure of
which has been incorporated herein by reference.
The power source may be current limited or otherwise controlled so
that undesired heating of the target tissue or surrounding
(non-target) tissue does not occur. In a presently preferred
embodiment of the present invention, current limiting inductors are
placed in series with each independent electrode terminal, where
the inductance of the inductor is in the range of 10 uH to 50,000
uH, depending on the electrical properties of the target tissue,
the desired tissue heating rate and the operating frequency.
Alternatively, capacitor-inductor (LC) circuit structures may be
employed, as described previously in co-pending PCT application No.
PCT/US94/05168, the complete disclosure of which is incorporated
herein by reference. Additionally, current limiting resistors may
be selected. Preferably, these resistors will have a large positive
temperature coefficient of resistance so that, as the current level
begins to rise for any individual electrode terminal in contact
with a low resistance medium (e.g., saline irrigant or conductive
gel), the resistance of the current limiting resistor increases
significantly, thereby minimizing the power delivery from said
electrode terminal into the low resistance medium (e.g., saline
irrigant or conductive gel).
It should be clearly understood that the invention is not limited
to electrically isolated electrode terminals, or even to a
plurality of electrode terminals. For example, the array of active
electrode terminals may be connected to a single lead that extends
through the instrument shaft to a power source of high frequency
current. Alternatively, the instrument may incorporate a single
electrode that extends directly through the instrument shaft or is
connected to a single lead that extends to the power source. The
active electrode may have a ball shape (e.g., for tissue
vaporization and desiccation), a twizzle shape (for vaporization
and needle-like cutting), a spring shape (for rapid tissue
debulking and desiccation), a twisted metal shape, an annular or
solid tube shape or the like. Alternatively, the electrode may
comprise a plurality of filaments, a rigid or flexible brush
electrode (for debulking a tumor, such as a fibroid, bladder tumor
or a prostate adenoma), a side-effect brush electrode on a lateral
surface of the shaft, a coiled electrode or the like. In one
embodiment, the instrument comprises a single active electrode
terminal that extends from an insulating member, e.g., ceramic, at
the distal end of the instrument. The insulating member is
preferably a tubular structure that separates the active electrode
terminal from a tubular or annular return electrode positioned
proximal to the insulating member and the active electrode.
Referring to FIG. 1, an exemplary electrosurgical system 11 for
treatment of tissue in the head and neck will now be described in
detail. Electrosurgical system 11 generally comprises an
electrosurgical handpiece or probe 10 connected to a power supply
28 for providing high frequency voltage to a target site and a
fluid source 21 for supplying electrically conducting fluid 50 to
probe 10. In addition, electrosurgical system 11 may include an
endoscope (not shown) with a fiber optic head light for viewing the
surgical site, particularly in sinus procedures or procedures in
the ear or the back of the mouth. The endoscope may be integral
with probe 10, or it may be part of a separate instrument. The
system 11 may also include a vacuum source (not shown) for coupling
to a suction lumen or tube 205 (see FIG. 2) in the probe 10 for
aspirating the target site.
As shown, probe 10 generally includes a proximal handle 19 and an
elongate shaft 18 having an array 12 of electrode terminals 58 at
its distal end. A connecting cable 34 has a connector 26 for
electrically coupling the electrode terminals 58 to power supply
23. The electrode terminals 58 are electrically isolated from each
other and each of the terminals 58 is connected to an active or
passive control network within power supply 28 by means of a
plurality of individually insulated conductors (not shown). A fluid
supply tube 15 is connected to a fluid tube 14 of probe 10 for
supplying electrically conducting fluid 50 to the target site.
Power supply 28 has an operator controllable voltage level
adjustment 30 to change the applied voltage level, which is
observable at a voltage level display 32. Power supply 28 also
includes first, second and third foot pedals 37, 38, 39 and a cable
36 which is removably coupled to power supply 28. The foot pedals
37, 38, 39 allow the surgeon to remotely adjust the energy level
applied to electrode terminals 58. In an exemplary embodiment,
first foot pedal 37 is used to place the power supply into the
"ablation" mode and second foot pedal 38 places power supply 28
into the "coagulation" mode. The third foot pedal 39 allows the
user to adjust the voltage level within the "ablation" mode. In the
ablation mode, a sufficient voltage is applied to the electrode
terminals to establish the requisite conditions for molecular
dissociation of the tissue (i.e., vaporizing a portion of the
electrically conductive fluid, ionizing charged particles within
the vapor layer and accelerating these charged particles against
the tissue). As discussed above, the requisite voltage level for
ablation will vary depending on the number, size, shape and spacing
of the electrodes, the distance in which the electrodes extend from
the support member, etc. Once the surgeon places the power supply
in the "ablation" mode, voltage level adjustment 30 or third foot
pedal 39 may be used to adjust the voltage level to adjust the
degree or aggressiveness of the ablation.
Of course, it will be recognized that the voltage and modality of
the power supply may be controlled by other input devices. However,
applicant has found that foot pedals are convenient methods of
controlling the power supply while manipulating the probe during a
surgical procedure.
In the coagulation mode, the power supply 28 applies a low enough
voltage to the electrode terminals (or the coagulation electrode)
to avoid vaporization of the electrically conductive fluid and
subsequent molecular dissociation of the tissue. The surgeon may
automatically toggle the power supply between the ablation and
coagulation modes by alternatively stepping on foot pedals 37, 38,
respectively. This allows the surgeon to quickly move between
coagulation and ablation in situ, without having to remove his/her
concentration from the surgical field or without having to request
an assistant to switch the power supply. By way of example, as the
surgeon is sculpting soft tissue in the ablation mode, the probe
typically will simultaneously seal and/or coagulation small severed
vessels within the tissue. However, larger vessels, or vessels with
high fluid pressures (e.g., arterial vessels) may not be sealed in
the ablation mode. Accordingly, the surgeon can simply step on foot
pedal 38, automatically lowering the voltage level below the
threshold level for ablation, and apply sufficient pressure onto
the severed vessel for a sufficient period of time to seal and/or
coagulate the vessel. After this is completed, the surgeon may
quickly move back into the ablation mode by stepping on foot pedal
37. A specific design of a suitable power supply for use with the
present invention can be found in U.S. Provisional Patent
Application 60/062,997, filed Oct. 23, 1997 (attorney docket no.
16238-007400), previously incorporated herein by reference.
FIGS. 2-5 illustrate an exemplary electrosurgical probe 90
constructed according to the principles of the present invention.
As shown in FIG. 2, probe 90 generally includes an elongated shaft
100 which may be flexible or rigid, a handle 204 coupled to the
proximal end of shaft 100 and an electrode support member 102
coupled to the distal end of shaft 100. Shaft 100 preferably
includes a bend 101 that allows the distal section of shaft 100 to
be offset from the proximal section and handle 204. This offset
facilitates procedures that require an endoscope, such as FESS,
because the endoscope can, for example, be introduced through the
same nasal passage as the shaft 100 without interference between
handle 204 and the eyepiece of the endoscope (see FIG. 11). Shaft
100 preferably comprises a plastic material that is easily molded
into the shape shown in FIG. 1.
In an alternative embodiment (see FIG. 6A), shaft 100 comprises an
electrically conducting material, usually metal, which is selected
from the group comprising tungsten, stainless steel alloys,
platinum or its alloys, titanium or its alloys, molybdenum or its
alloys, and nickel or its alloys. In this embodiment, shaft 100
includes an electrically insulating jacket 108, which is typically
formed as one or more electrically insulating sheaths or coatings,
such as polytetrafluoroethylene, polyimide, and the like. The
provision of the electrically insulating jacket over the shaft
prevents direct electrical contact between these metal elements and
any adjacent body structure or the surgeon. Such direct electrical
contact between a body structure (e.g., tendon) and an exposed
electrode could result in unwanted heating and necrosis of the
structure at the point of contact causing necrosis.
Handle 204 typically comprises a plastic material that is easily
molded into a suitable shape for handling by the surgeon. Handle
204 defines an inner cavity (not shown) that houses the electrical
connections 250 (FIG. 5), and provides a suitable interface for
connection to an electrical connecting cable 22 (see FIG. 1).
Electrode support member 102 extends from the distal end of shaft
100 (usually about 1 to 20 mm), and provides support for a
plurality of electrically isolated electrode terminals 104 (see
FIGS. 3 and 4). As shown in FIG. 2, a fluid tube 233 extends
through an opening in handle 204, and includes a connector 235 for
connection to a fluid supply source, for supplying electrically
conductive fluid to the target site. Depending on the configuration
of the distal surface of shaft 100, fluid tube 233 may extend
through a single lumen (not shown) in shaft 100, or it may be
coupled to a plurality of lumens (also not shown) that extend
through shaft 100 to a plurality of openings at its distal end. In
the representative embodiment, fluid tube 233 extends along the
exterior of shaft 100 to a point just proximal of return electrode
112 (see FIG. 4). In this embodiment, the fluid is directed through
an opening 237 past return electrode 112 to the electrode terminals
104. Probe 90 may also include a valve 17 (FIG. 1) or equivalent
structure for controlling the flow rate of the electrically
conducting fluid to the target site.
As shown in FIG. 2, the distal portion of shaft 100 is preferably
bent to improve access to the operative site of the tissue being
treated. Electrode support member 102 has a substantially planar
tissue treatment surface 212 (FIGS. 5A and 5B) that is usually at
an angle of about 10 to 90 degrees relative to the longitudinal
axis of shaft 100, preferably about 30 to 60 degrees and more
preferably about 45 degrees. In alternative embodiments, the distal
portion of shaft 100 comprises a flexible material which can be
deflected relative to the longitudinal axis of the shaft. Such
deflection may be selectively induced by mechanical tension of a
pull wire, for example, or by a shape memory wire that expands or
contracts by externally applied temperature changes. A more
complete description of this embodiment can be found in PCT
International Application, U.S.
National Phase Serial No. PCT/US94/05168, filed on May 10, 1994
(Attorney Docket 16238-000440), the complete disclosure of which
has previously been incorporated herein by reference.
The bend in the distal portion of shaft 100 is particularly
advantageous in the treatment of sinus tissue as it allows the
surgeon to reach the target tissue within the nose as the shaft 100
extends through the nasal passage. Of course, it will be recognized
that the shaft may have different angles depending on the
procedure. For example, a shaft having a 90.degree. bend angle may
be particularly useful for accessing tissue located in the back
portion of the mouth and a shaft having a 10.degree. to 30.degree.
bend angle may be useful for accessing tissue near or in the front
portion of the mouth or nose In the embodiment shown in FIGS. 2-5,
probe 90 includes a return electrode 112 for completing the current
path between electrode terminals 104 and a high frequency power
supply 28 (see FIG. 1). As shown, return electrode 112 preferably
comprises an annular conductive band coupled to the distal end of
shaft 100 slightly proximal to tissue treatment surface 212 of
electrode support member 102, typically about 0.5 to 10 mm and more
preferably about 1 to 10 mm. Return electrode 112 is coupled to a
connector 258 that extends to the proximal end of probe 10, where
it is suitably connected to power supply 10 (FIG. 1).
As shown in FIG. 2, return electrode 112 is not directly connected
to electrode terminals 104. To complete this current path so that
electrode terminals 104 are electrically connected to return
electrode 112, electrically conducting fluid (e.g., isotonic
saline) is caused to flow therebetween. In the representative
embodiment, the electrically conducting fluid is delivered through
fluid tube 233 to opening 237, as described above. Alternatively,
the fluid may be delivered by a fluid delivery element (not shown)
that is separate from probe 90. In arthroscopic surgery, for
example, the body cavity will be flooded with isotonic saline and
the probe 90 will be introduced into this flooded cavity.
Electrically conducting fluid will be continually resupplied to
maintain the conduction path between return electrode 112 and
electrode terminals 104.
In alternative embodiments, the fluid path may be formed in probe
90 by, for example, an inner lumen or an annular gap between the
return electrode and a tubular support member within shaft 100 (see
FIG. 6). This annular gap may be formed near the perimeter of the
shaft 100 such that the electrically conducting fluid tends to flow
radially inward towards the target site, or it may be formed
towards the center of shaft 100 so that the fluid flows radially
outward. In both of these embodiments, a fluid source (e.g., a bag
of fluid elevated above the surgical site or having a pumping
device), is coupled to probe 90 via a fluid supply tube (not shown)
that may or may not have a controllable valve. A more complete
description of an electrosurgical probe incorporating one or more
fluid lumen(s) can be found in parent application Serial No.
08/485,219, filed on Jun. 7, 1995, now U.S. Pat. No. 5,697,281, the
complete disclosure of which has previously been incorporated
herein by reference.
Referring to FIG. 3, the electrically isolated electrode terminals
104 are spaced apart over tissue treatment surface 212 of electrode
support member 102. The tissue treatment surface and individual
electrode terminals 104 will usually have dimensions within the
ranges set forth above. In the representative embodiment, the
tissue treatment surface 212 has an oval cross-sectional shape with
a length in the range of 1 mm to 20 mm and a width in the range
from 0.3 mm to 7 mm. The oval cross-sectional shape accommodates
the bend in the distal portion of shaft 100. The individual
electrode terminals 104 preferably extend outward from tissue
treatment surface 212 by a distance of about 0.1 to 4 mm. usually
about 0.2 to 2 mm. Applicant has found that this configuration
increases the high (electric field intensities and associated
current densities around electrode terminals 104 to facilitate the
ablation of tissue as described in detail above.
In the embodiment of FIGS. 2-5, the probe includes a single, larger
opening 209 in the center of tissue treatment surface 212, and a
plurality of electrode terminals (e.g., about 3-15) around the
perimeter of surface 212 (see FIG. 3). Alternatively, the probe may
include a single, annular, or partially annular, electrode terminal
at the perimeter of the tissue treatment surface. The central
opening 209 is coupled to a suction lumen (not shown) within shaft
100 and a suction tube 211 (FIG. 2) for aspirating tissue, fluids
and/or gases from the target site. In this embodiment, the
electrically conductive fluid generally flows radially inward past
electrode terminals 104 and then back through the opening 209.
Aspirating the electrically conductive fluid during surgery allows
the surgeon to see the target site, and it prevents the fluid from
flowing into the patient's body, e.g., through the sinus passages,
down the patient's throat or into the ear canal.
Of course, it will be recognized that the distal tip of probe may
have a variety of different configurations. For example, the probe
may include a plurality of openings 209 around the outer perimeter
of tissue treatment surface 212 (see FIG. 6B). In this embodiment,
the electrode terminals 104 extend from the center of tissue
treatment surface 212 radially inward from openings 209. The
openings are suitably coupled to fluid tube 233 for delivering
electrically conductive fluid to the target site, and suction tube
211 for aspirating the fluid after it has completed the conductive
path between the return electrode 112 and the electrode terminals
104.
FIG. 5 illustrates the electrical connections 250 within handle 204
for coupling electrode terminals 104 and return electrode 112 to
the power supply 28. As shown, a plurality of wires 252 extend
through shaft 100 to couple terminals 104 to a plurality of pins
254, which are plugged into a connector block 256 for coupling to a
connecting cable 22 (FIG. 1). Similarly, return electrode 112 is
coupled to connector block 256 via a wire 258 and a plug 260.
According to the present invention, the probe 90 further includes
an identification element that is characteristic of the particular
electrode assembly so that the same power supply 28 can be used for
different electrosurgical operations. In one embodiment, for
example, the probe 90 includes a voltage reduction element or a
voltage reduction circuit for reducing the voltage applied between
the electrode terminals 104 and the return electrode 112. The
voltage reduction element serves to reduce the voltage applied by
the power supply so that the voltage between the electrode
terminals and the return electrode is low enough to avoid excessive
power dissipation into the electrically conducting medium and/or
ablation of the soft tissue at the target site. The voltage
reduction element primarily allows the electrosurgical probe 90 to
be compatible with other ArthroCare generators that are adapted to
apply higher voltages for ablation or vaporization of tissue. For
contraction of tissue, for example, the voltage reduction element
will serve to reduce a voltage of about 100 to 135 volts rms (which
is a setting of 1 on the ArthroCare Model 970 and 980 (i.e., 2000)
Generators) to about 45 to 60 volts rms, which is a suitable
voltage for contraction of tissue without ablation (e.g., molecular
dissociation) of the tissue.
Of course, for some procedures, such as endoscopic sinus surgery,
the probe will typically not require a voltage reduction element.
Alternatively, the probe may include a voltage increasing element
or circuit, if desired.
In the representative embodiment, the voltage reduction element is
a dropping capacitor 262 which has first leg 264 coupled to the
return electrode wire 258 and a second leg 266 coupled to connector
block 256. Of course, the capacitor may be located in other places
within the system, such as in, or distributed along the length of,
the cable, the generator, the connector, etc. In addition, it will
be recognized that other voltage reduction elements, such as
diodes, transistors, inductors, resistors, capacitors or
combinations thereof, may be used in conjunction with the present
invention. For example, the probe 90 may include a coded resistor
(not shown) that is constructed to lower the voltage applied
between return electrode 112 and electrode terminals 104 to a
suitable level for contraction of tissue. In addition, electrical
circuits may be employed for this purpose.
Alternatively or additionally, the cable 22 that couples the power
supply 10 to the probe 90 may be used as a voltage reduction
element. The cable has an inherent capacitance that can be used to
reduce the power supply voltage if the cable is placed into the
electrical circuit between the power supply, the electrode
terminals and the return electrode. In this embodiment, the cable
22 may be used alone, or in combination with one of the voltage
reduction elements discussed above, e.g., a capacitor.
Further, it should be noted that the present invention can be used
with a power supply that is adapted to apply a voltage within the
selected range for treatment of tissue. In this embodiment, a
voltage reduction element or circuitry may not be desired.
FIGS. 7A-7C schematically illustrate the distal portion of three
different embodiments of probe 90 according to the present
invention. As shown in 7A, electrode terminals 104 are anchored in
a support marix 102 of suitable insulating material (e.g., ceramic
or glass material, such as alumina, zirconia and the like) which
could be formed at the time of manufacture in a flat, hemispherical
or other shape according to the requirements of a particular
procedure. The preferred support matrix material is alumina,
available from Kyocera Industrial Ceramics Corporation, Elkgrove,
Ill., because of its high thermal conductivity, good electrically
insulative properties, high flexural modulus, resistance to carbon
tracking, biocompatibility, and high melting point. The support
matrix 102 is adhesively joined to a tubular support member 78 that
extends most or all of the distance between matrix 102 and the
proximal end of probe 90. Tubular member 78 preferably comprises an
electrically insulating material, such as an epoxy or
silicone-based material.
In a preferred construction technique, electrode terminals 104
extend through pre-formed openings in the support matrix 102 so
that they protrude above tissue treatment surface 212 by the
desired distance. The electrodes are then bonded to the tissue
treatment surface 212 of support matrix 102, typically by an
inorganic sealing material 80. Sealing material 80 is selected to
provide effective electrical insulation, and good adhesion to both
the alumina matrix 102 and the platinum or titanium electrode
terminals. Sealing material 80 additionally should have a
compatible thermal expansion coefficient and a melting point well
below that of platinum or titanium and alumina or zirconia,
typically being a glass or glass ceramic.
In the embodiment shown in FIG. 7A, return electrode 112 comprises
an annular member positioned around the exterior of shaft 100 of
probe 90. Return electrode 90 may fully or partially circumscribe
tubular support member 78 to form an annular gap 54 therebetween
for flow of electrically conducting liquid 50 therethrough, as
discussed below. Gap 54 preferably has a width in the range of 0.25
mm to 4 mm. Alternatively, probe may include a plurality of
longitudinal ribs between support member 78 and return electrode
112 to form a plurality of fluid lumens extending along the
perimeter of shaft 100. In this embodiment, the plurality of lumens
will extend to a plurality of openings.
Return electrode 112 is disposed within an electrically insulative
jacket 18, which is typically formed as one or more electrically
insulative sheaths or coatings, such as polytetrafluoroethylene,
polyamide, and the like. The provision of the electrically
insulative jacket 18 over return electrode 112 prevents direct
electrical contact between return electrode 56 and any adjacent
body structure. Such direct electrical contact between a body
structure (e.g., tendon) and an exposed electrode member 112 could
result in unwanted heating and necrosis of the structure at the
point of contact causing necrosis.
As shown in FIG. 7A, return electrode 112 is not directly connected
to electrode terminals 104. To complete this current path so that
terminals 104 are electrically connected to return electrode 112,
electrically conducting liquid 50 (e.g., isotonic saline) is caused
to flow along fluid path(s) 83. Fluid path 83 is formed by annular
gap 54 between outer return electrode 112 and tubular support
member. The electrically conducting liquid 50 flowing through fluid
path 83 provides a pathway for electrical current flow between
electrode terminals 104 and return electrode 112, as illustrated by
the current flux lines 60 in FIG. 6A. When a voltage difference is
applied between electrode terminals 104 and return electrode 112,
high electric field intensities will be generated at the distal
tips of terminals 104 with current flow from terminals 104 through
the target tissue to the return electrode, the high electric field
intensities causing ablation of tissue 52 in zone 88.
FIG. 7B illustrates another alternative embodiment of
electrosurgical probe 90 which has a return electrode 112
positioned within tubular member 78. Return electrode 112 is
preferably a tubular member defining an inner lumen 57 for allowing
electrically conducting liquid 50 (e.g., isotonic saline) to flow
therethrough in electrical contact with return electrode 112. In
this embodiment, a voltage difference is applied between electrode
terminals 104 and return electrode 112 resulting in electrical
current flow through the electrically conducting liquid 50 as shown
by current flux lines 60 (FIG. 3). As a result of the applied
voltage difference and concomitant high electric field intensities
at the tips of electrode terminals 104, tissue 52 becomes ablated
or transected in zone 88.
FIG. 7C illustrates another embodiment of probe 90 that is a
combination of the embodiments in FIGS. 7A and 7B. As shown, this
probe includes both an inner lumen 57 and an outer gap or plurality
of outer lumens 54 for flow of electrically conductive fluid. In
this embodiment, the return electrode 112 may be positioned within
tubular member 78 as in FIG. 7B, outside of tubular member 78 as in
FIG. 7A, or in both locations.
FIG. 9 illustrates another embodiment of probe 90 where the distal
portion of shaft 100 is bent so that electrode terminals extend
transversely to the shaft. Preferably, the distal portion of shaft
100 is perpendicular to the rest of the shaft so that tissue
treatment surface 212 is generally parallel to the shaft axis. In
this embodiment, return electrode 112 is mounted to the outer
surface of shaft 100 and is covered with an electrically insulating
jacket 18. The electrically conducting fluid 50 flows along flow
path 83 through return electrode 112 and exits the distal end of
electrode 112 at a point proximal of tissue treatment surface 212.
The fluid is directed exterior of shaft to surface 212 to create a
return current path from electrode terminals 104, through the fluid
50, to return electrode 12, as shown by current flux lines 60.
FIG. 10 illustrates another embodiment of the invention where
electrosurgical system 11 further includes a liquid supply
instrument 64 for supplying electrically conducting fluid 50
between electrode terminals 104 and return electrode 112. Liquid
supply instrument 64 comprises an inner tubular member or return
electrode 112 surrounded by an electrically insulating jacket 18.
Return electrode 112 defines an inner passage 83 for flow of fluid
50. As shown in FIG. 8, the distal portion of instrument 64 is
preferably bent so that liquid 50 is discharged at an angle with
respect to instrument 64. This allows the surgical team to position
liquid supply instrument 64 adjacent tissue treatment surface 212
with the proximal portion of supply instrument 64 oriented at a
similar angle to probe 90.
The present invention is not limited to an electrode array disposed
on a relatively planar surface at the distal tip of probe 90, as
described above. Referring to FIGS. 8A and 8B, an alternative probe
90 includes a pair of electrodes 105a, 105b mounted to the distal
end of shaft 100. Electrodes 105a, 105b are electrically connected
to power supply as described above and preferably have tips 107a,
107b with a screwdriver shape. The screwdriver shape provides a
greater amount of "edges" to electrodes 105a, 105b, to increase the
electric field intensity and current density at the edges and
thereby improve the cutting ability as well as the ability to limit
bleeding from the incised tissue (i.e., hemostasis).
FIGS. 11-13 illustrate a method for treating nasal or sinus
blockages, e.g., chronic sinusitis, according to the present
invention. In these procedures, the polyps, turbinates or other
sinus tissue may be ablated or reduced (e.g., by tissue
contraction) to clear the blockage and/or enlarge the sinus cavity
to reestablish normal sinus function. For example, in chronic
rhinitis, which is a collective term for chronic irritation or
inflammation of the nasal mucosa with hypertrophy of the nasal
mucosa, the inferior turbinate may be reduced by ablation or
contraction. Alternatively, a turbinectomy or mucotomy may be
performed by removing a strip of tissue from the lower edge of the
inferior turbinate to reduce the volume of the turbinate. For
treating nasal polypi, which comprises benign pedicled or sessile
masses of nasal or sinus mucosa caused by inflammation, the nasal
polypi may be contracted or shrunk, or ablated by the method of the
present invention. For treating severe sinusitis, a frontal sinus
operation may be performed to introduce the electrosurgical probe
to the site of blockage. The present invention may also be used to
treat diseases of the septum, e.g., ablating or resecting portions
of the septum for removal, straightening or reimplantation of the
septum.
The present invention is particularly useful in functional
endoscopic sinus surgery (FESS) in the treatment of sinus disease.
In contrast to prior art microdebriders, the electrosurgical probe
of the present invention effects hemostasis of severed blood
vessels, and allows the surgeon to precisely remove tissue with
minimal or no damage to surrounding tissue, bone, cartilage or
nerves. By way of example and not limitation, the present invention
may be used for the following procedures: (1) uncinectomy or medial
displacement or removal of portions of the middle turbinate; (2)
maxillary, sphenoid or ethmoid sinusotomies or enlargement of the
natural ostium of the maxillary, sphenoid, or ethmoid sinuses,
respectively; (3) frontal recess dissections, in which polypoid or
granulation tissue are removed; (4) polypectomies, wherein polypoid
tissue is removed in the case of severe nasal polyposis; (5) concha
bullosa resections or the thinning of polypoid middle turbinate;
(6) septoplasty; and the like.
FIGS. 11-13 schematically illustrate an endoscopic sinus surgery
(FESS) procedure according to the present invention. As shown in
FIG. 11, an endoscope 300 is first introduced through one of the
nasal passages 301 to allow the surgeon to view the target site,
e.g., the sinus cavities. As shown, the endoscope 300 will usually
comprise a thin metal tube 302 with a lens (not shown) at the
distal end 304, and an eyepiece 306 at the proximal end 308. As
shown in FIG. 2, the probe shaft 100 (not shown in FIG. 11) has a
bend 101 to facilitate use of both the endoscope and the probe 90
in the same nasal passage (i.e., the handles of the two instruments
do not interfere with each other in this embodiment).
Alternatively, the endoscope may be introduced transorally through
the inferior soft palate to view the nasopharynx. Suitable nasal
endoscopes for use with the present invention are described in U.S.
Pat. Nos. 4,517,962, 4,844,052, 4,881,523 and 5,167,220, the
complete disclosures of which are incorporated herein by reference
for all purposes.
Alternatively, the endoscope 300 may include a sheath (not shown)
having an inner lumen for receiving the electrosurgical probe shaft
100. In this embodiment, the shaft 100 will extend through the
inner lumen to a distal opening in the endoscope. The shaft will
include suitable proximal controls for manipulation of its distal
end during the surgical procedure.
As shown in FIG. 12, the distal end of probe 90 is introduced
through nasal passage 301 into the nasal cavity 303 (endoscope 300
is not shown in FIG. 12). Depending on the location of the
blockage, the electrode terminals 104 will be positioned adjacent
the blockage in the nasal cavity 303, or in one of the paranasal
sinuses 305, 307. Note that only the frontal sinus 305 and the
sphenoidal sinus 307 are shown in FIG. 12, but the procedure is
also applicable to the ethmoidal and maxillary sinuses. Once the
surgeon has reached the point of major blockage, electrically
conductive fluid is delivered through tube 233 and opening 237 to
the tissue (see FIG. 2). The fluid flows past the return electrode
112 to the electrode terminals 104 at the distal end of the shaft.
The rate of fluid flow is controlled with valve 17 (FIG. 1) such
that the zone between the tissue and electrode support 102 is
constantly immersed in the fluid. The power supply 28 is then
turned on and adjusted such that a high frequency voltage
difference is applied between electrode terminals 104 and return
electrode 112. The electrically conductive fluid provides the
conduction path (see current flux lines) between electrode
terminals 104and the return electrode 112.
FIGS. 13A and 13B illustrate the removal of sinus tissue in more
detail As shown, the high frequency voltage is sufficient to
convert the electrically conductive fluid (not shown) between the
target tissue 302 and electrode terminal(s)104 into an ionized
vapor layer 312 or plasma. As a result of the applied voltage
difference between electrode terminal(s) 104 and the target tissue
302 (i.e., the voltage gradient across the plasma layer 312),
charged particles 315 in the plasma (viz., electrons) are
accelerated towards the tissue. At sufficiently high voltage
differences, these charged particles 315 gain sufficient energy to
cause dissociation of the molecular bonds within tissue structures.
This molecular dissociation is accompanied by the volumetric
removal (i.e., ablative sublimation) of tissue and the production
of low molecular weight gases 314, such as oxygen, nitrogen, carbon
dioxide, hydrogen and methane. The short range of the accelerated
charged particles 315 within the tissue confines the molecular
dissociation process to the surface layer to minimize damage and
necrosis to the underlying tissue 320.
During the process, the gases 314 will be aspirated through opening
209 and suction tube 211 to a vacuum source. In addition, excess
electrically conductive fluid, and other fluids (e.g., blood) will
be aspirated from the target site 300 to facilitate the surgeon's
view. Daring ablation of the tissue, the residual heat generated by
the current flux lines (typically less than 150.degree. C.), will
usually be sufficient to coagulate any severed blood vessels at the
site. If not, the surgeon may switch the power supply 28 into the
coagulation mode by lowering the voltage to a level below the
threshold for fluid vaporization, as discussed above. This
simultaneous hemostasis results in less bleeding and facilitates
the surgeon's ability to perform the procedure. Once the blockage
has been removed, aeration and drainage are reestablished to allow
the sinuses to heal and return to their normal function.
Another advantage of the present invention is the ability to
precisely ablate layers of sinus tissue without causing necrosis or
thermal damage to the underlying and surrounding tissues, nerves
(e.g., the optic nerve) or bone. In addition, the voltage can be
controlled so that the energy directed to the target site is
insufficient to ablate bone or adipose tissue (which generally has
a higher impedance than the target sinus tissue). In this manner,
the surgeon can literally clean the tissue off the bone, without
ablating or otherwise effecting significant damage to the bone.
Methods for treating air passage disorders according to the present
invention will now be described. In these embodiments, an
electrosurgical probe such as one described above can be used to
ablate targeted masses including, but not limited to, the tongue,
tonsils, turbinates, soft palate tissues (e.g., the uvula), hard
tissue and mucosal tissue. In one embodiment, selected portions of
the tongue 314 are removed to treat sleep apnea. In this method,
the distal end of an electrosurgical probe 90 is introduced into
the patient's mouth 310, as shown in FIG. 14. An endoscope (not
shown), or other type of viewing device, may also be introduced, or
partially introduced, into the mouth 310 to allow the surgeon to
view the procedure (the viewing device may be integral with, or
separate from, the electrosurgical probe). The electrode terminals
104 are positioned adjacent to or against the back surface 316 of
the tongue 314, and electrically conductive fluid is delivered to
the target site, as described above. The power supply 28 is then
activated to remove selected portions of the back of the tongue
314, as described above, without damaging sensitive structures,
such as nerves, and the bottom portion of the tongue 314.
In another embodiment, the electrosurgical probe of the present
invention can be used to ablate and/or contract soft palate tissue
to treat snoring disorders. In particular, the probe is used to
ablate or shrink sections of the uvula 320 without causing unwanted
tissue damage under and around the selected sections of tissue. For
tissue contraction, a sufficient voltage difference is applied
between the electrode terminals 104 and the return electrode 112 to
elevate the uvula tissue temperature from normal body temperatures
(e.g., 37.degree. C.) to temperatures in the range of 45.degree. C.
to 90.degree. C., preferably in the range from 60.degree. C. to
70.degree. C. This temperature elevation causes contraction of the
collagen connective fibers within the uvula tissue.
In one method of tissue contraction according to the present
invention, an electrically conductive fluid is delivered to the
target site as described above, and heated to a sufficient
temperature to induce contraction or shrinkage of the collagen
fibers in the target tissue. The electrically conducting fluid is
heated to a temperature sufficient to substantially irreversibly
contract the collagen fibers, which generally requires a tissue
temperature in the range of about 45.degree. C. to 90.degree. C.,
usually about 60.degree. C. to 70.degree. C. The fluid is heated by
applying high frequency electrical energy to the electrode
terminal(s) in contact with the electrically conducting fluid. The
current emanating from the electrode terminal(s) 104 heats the
fluid and generates a jet or plume of heated fluid, which is
directed towards the target tissue. The heated fluid elevates the
temperature of the collagen sufficiently to cause hydrothermal
shrinkage of the collagen fibers. The return electrode 112 draws
the electric current away from the tissue site to limit the depth
of penetration of the current into the tissue, thereby inhibiting
molecular dissociation and breakdown of the collagen tissue and
minimizing or completely avoiding damage to surrounding and
underlying tissue structures beyond the target tissue site. In an
exemplary embodiment, the electrode terminal(s) 104 are held away
from the tissue a sufficient distance such that the RF current does
not pass into the tissue at all, but rather passes through the
electrically conducting fluid back to the return electrode. In this
embodiment, the primary mechanism for imparting energy to the
tissue is the heated fluid, rather than the electric current.
In an alternative embodiment, the electrode terminal(s) 104 are
brought into contact with, or close proximity to, the target tissue
so that the electric current passes directly into the tissue to a
selected depth. In this embodiment, the return electrode draws the
electric current away from the tissue site to limit its depth of
penetration into the tissue. Applicant has discovered that the
depth of current penetration also can be varied with the
electrosurgical system of the present invention by changing the
frequency of the voltage applied to the electrode terminal and the
return electrode. This is because the electrical impedance of
tissue, is known to decrease with increasing frequency due to the
electrical properties of cell membranes which surround electrically
conductive cellular fluid. At lower frequencies (e.g., less than
350 kHz), the higher tissue impedance, the presence of the return
electrode and the electrode terminal configuration of the present
invention (discussed in detail below) cause the current flux lines
to penetrate less deeply resulting in a smaller depth of a issue
heating. In an exemplary embodiment, an operating frequency of
about 100 to 200 kHz is applied to the electrode terminal(s) to
obtain shallow depths of collagen shrinkage (e.g., usually less
than 1.5 mm and preferably less than 0.5 mm).
In another aspect of the invention, the size (e.g., diameter or
principal dimension) of the electrode terminals employed for
treating the tissue are selected according to the intended depth of
tissue treatment. As described previously in copending patent
application PCT International Application, U.S. National Phase
Serial No. PCT/US94/05168, the depth of current penetration into
tissue increases with increasing dimensions of an individual active
electrode (assuming other factors remain constant, such as the
frequency of the electric current, the return electrode
configuration, etc.). The depth of current penetration (which
refers to the depth at which the current density is sufficient to
effect a change in the tissue, such as collagen shrinkage,
irreversible necrosis, etc.) is on the order of the active
electrode diameter for the bipolar configuration of the present
invention and operating at a frequency of about 100 kHz to about
200 kHz. Accordingly, for applications requiring a smaller depth of
current penetration, one or more electrode terminals of smaller
dimensions would be selected. Conversely, for applications
requiring a greater depth of current penetration, one or more
electrode terminals of larger dimensions would be selected.
In addition to the above procedures, the system and method of the
present invention may be used for treating a variety of disorders
in the mouth 310, pharynx 330, larynx 335, hypopharynx, trachea
340, esophagus 350 and the neck 360. For example, tonsillar
hyperplasis or other tonsil disorders may be treated with a
tonsillectomy by partially ablating the lymphoepithelial tissue.
This procedure is usually carried out under intubation anesthesia
with the head extended. An incision is made in the anterior faucial
pillar, and the connective tissue layer between the tonsillar
parenchyma and the pharyngeal constrictor muscles is demonstrated.
The incision may be made with conventional scalpels, or with the
electrosurgical probe of the present invention. The tonsil is then
freed by ablating through the upper pole to the base of the tongue,
preserving the faucial pillars. The probe ablates the tissue, while
providing simultaneous hemostasis of severed blood vessels in the
region. Similarly, adenoid hyperplasis, or nasal obstruction
leading to mouth breathing difficulty, can be treated in an
adenoidectomy by separating (e.g., resecting or ablating) the
adenoid from the base of the nasopharynx.
Other pharyngeal disorders can be treated according to the present
invention. For example, hypopharyngeal diverticulum involves small
pouches that form within the esophagus immediately above the
esophageal opening. The sac of the pouch may be removed
endoscopically according to the present invention by introducing a
rigid esophagoscope, and isolating the sac of the pouch. The
cricopharyngeus muscle is then divided, and the pouch is ablated
according to the present invention. Tumors within the mouth and
pharynx, such as hemangionmas, lymphangiomas, papillomas, lingual
thyroid tumors, or malignant tumors, may also be removed according
to the present invention.
Other procedures of the present invention include removal of vocal
cord polyps and lesions and partial or total laryngectomies. In the
latter procedure, the entire larynx is removed from the base of the
tongue to the trachea, if necessary with removal of parts of the
tongue, the pharynx, the trachea and the thyroid gland.
Tracheal stenosis may also be treated according to the present
invention. Acute and chronic stenoses within the wall of the
trachea may cause coughing, cyanosis and choking.
Referring to FIGS. 15-17, the electrosurgical device according to
the present invention may also be configured as a catheter system
400. As shown in FIG. 15, a catheter system 400 generally comprises
an electrosurgical catheter 460 connected to a power supply 28 by
an interconnecting cable 486 for providing high frequency voltage
to a target tissue and an irrigant reservoir or source 600 for
providing electrically conducting fluid to the target site.
Catheter 460 generally comprises an elongate, flexible shaft body
462 including a tissue removing or ablating region 464 at the
distal end of body 462. The proximal portion o catheter 460
includes a multi-lumen fitment 614 which provides for
interconnections between lumens and electrical leads within
catheter 460 and conduits and cables proximal to fitment 614. By
way of example, a catheter electrical connector 496 is removably
connected to a distal cable connector 494 which, in turn, is
removably connectable to generator 28 through connector 492. One or
more electrically conducting lead wires (not shown) within catheter
460 extend between one or more active electrodes 463 at tissue
ablating region 464 and one or more corresponding electrical
terminals (also not shown) in catheter connector 496 via active
electrode cable branch 487. Similarly, one or more return
electrodes 466 at tissue ablating region 464 are coupled to a
return electrode cable branch 489 of catheter connector 496 by lead
wires (not shown). Of course, a single cable branch (not shown) may
be used for both active and return electrodes.
Catheter body 462 may include reinforcing fibers or braids (not
shown) in the walls of at least the distal ablation region 464 of
body 462 to provide responsive torque control for rotation of
electrode terminals during tissue engagement. This rigid portion of
the catheter body 462 preferably extends only about 7 to 10 mm
while the remainder of the catheter body 462 is flexible to provide
good trackability during advancement and positioning of the
electrodes adjacent target tissue.
Conductive fluid 30 is provided to tissue ablation region 464 of
catheter 460 via a lumen (not shown in FIG. 15) within catheter
460. Fluid is supplied to lumen from the source along a conductive
fluid supply line 602 and a conduit 603, which is coupled to the
inner catheter lumen at multi-lumen fitment 114. The source of
conductive fluid (e.g., isotonic saline) may be an irrigant pump
system (not shown) or a gravity-driven supply, such as an irrigant
reservoir 600 positioned several feet above the level of the
patient and tissue ablating region 8. A control valve 604 may be
positioned at the interface of fluid supply line 602 and conduit
603 to allow manual control of the flow rate of electrically
conductive fluid 30. Alternatively, a metering pump or flow
regulator may be used to precisely control the flow rate of the
conductive fluid.
System 400 further includes an aspiration or vacuum system (not
shown) to aspirate liquids and gases from the target site. The
aspiration system will usually comprise a source of vacuum, coupled
to fitment 614 by a aspiration connector 605.
FIGS. 16 and 17 illustrate the working end 464 of an
electrosurgical catheter 460 constructed according to the
principles of the present invention. As shown in FIG. 16, catheter
460 generally includes an elongated shaft 462 which may be flexible
or rigid, and an electrode support member 620 coupled to the distal
end of shaft 462. Electrode support member 620 extends from the
distal end of shaft 462 (usually about 1 to 20 mm), and provides
support for a plurality of electrically isolated electrode
terminals 463. Electrode support member 620 and electrode terminals
462 are preferably secured to a tubular support member 626 within
shaft 460 by adhesive 630.
The electrode terminals 463 may be constructed using round, square,
rectangular or other shaped conductive metals. By way of example,
the electrode terminal materials may be selected from the group
including stainless steel, tungsten and its alloys, molybdenum and
its alloys, titanium and its alloys, nickel-based alloys, as well
as platinum and its alloys. Electrode support member 620 is
preferably a ceramic, glass or glass/ceramic composition (e.g.,
aluminum oxide, titanium nitride). Alternatively, electrode support
member 620 may include the use of high-temperature biocompatible
plastics such as polyether-ether-keytone (PEEK) manufactured by
Vitrex International Products, Inc. or polysulfone manufactured by
GE Plastics. The adhesive 630 may, by way of example, be an epoxy
(e.g., Master Bond EP42HT) or a silicone-based adhesive.
As shown in FIG. 17B, a total of 7 circular active electrodes or
electrode terminals 463 are shown in a symmetrical pattern having
an active electrode diameter, D.sub.1 in the range from 0.05 mm to
1.5 mm, more preferably in the range from 0.1 mm to 0.75 mm. The
interelectrode spacings, W.sub.1 and W.sub.2 are preferably in the
range from 0.1 mm to 1.5 mm and more preferably in the range from
0.2 mm to 0.75 mm. The distance between the outer perimeter of the
electrode terminal 463 and the perimeter of the electrode support
member, W.sub.3 is preferably in the range from 0.1 mm to 1.5 mm
and more preferably in the range from 0.2 mm to 0.75 mm. The
overall diameter, D.sub.2 of the working end 464 of catheter body
462 is preferably in the range from 0.5 mm to 10 mm and more
preferably in the range from 0.5 mm to 5 mm. As discussed above,
the shape of the active electrodes may be round, square,
triangular, hexagonal, rectangular, tubular, flat strip and the
like and may be arranged in a circularly symmetric pattern or may,
by way of example, be arranged in a rectangular pattern, square
pattern, or strip.
Catheter body 462 includes a tubular cannula 626 extending along
body 462 radially outward from support member 620 and electrode
terminals 463. The material for cannula 626 may be advantageously
selected from a group of electrically conductive metals so that the
cannula 626 functions as both a structural support member for the
array of electrode terminals 463 as well as a return electrode 624.
The support member 626 is connected to an electrical lead wire (not
shown) at its proximal end within a connector housing (not shown)
and continues via a suitable connector to power supply 28 to
provide electrical continuity between one output pole of high
frequency generator 28 and said return electrode 624. The cannula
626 may be selected from the group including stainless steel,
copper-based alloys, titanium or its alloys, and nickel-based
alloys. The thickness of the cannula 626 is preferably in the range
from 0.08 mm to 1.0 mm and more preferably in the range from 0.1 mm
to 0.4 mm.
As shown in FIG. 16, cannula 626 is covered with an electrically
insulating sleeve 608 to protect the patient's body from the
electric current. Electrically insulating sleeve 608 may be a
coating (e.g., nylon) or heat shrinkable plastic (e.g.,
fluropolymer or polyester). The proximal portion of the cannula 626
is left exposed to function as the return electrode 624. The length
of the return electrode 624, L.sub.5 is preferably in the range
from 1 mm to 30 mm and more preferably in the range from 2 mm to 20
mm. The spacing between the most distal portion of the return
electrode 624 and the plane of the tissue treatment surface 622 of
the electrode support member 620, L.sub.1 is preferably in the
range from 0.5 mm to 30 mm and more preferably in the range from 1
mm to 20 mm. The thickness of the electrically insulating sleeve
608 is preferably in the range from 0.01 mm to 0.5 mm and more
preferably in the range from 0.02 mm to 0.2 mm.
In the representative embodiment, the fluid path is formed in
catheter by an inner lumen 627 or annular gap between the return
electrode 624 and a second tubular support member 623 within shaft
460. This annular gap may be formed near the perimeter of the shaft
460 as shown in FIG. 16 such that the electrically conducting fluid
tends to flow radially inward towards the target site, or it may be
formed towards the center of shaft 460 (not shown) so that the
fluid flows radially outward. In both of these embodiments, a fluid
source (e.g., a bag of fluid elevated above the surgical site or
having a pumping device), is coupled to catheter 460 via a fluid
supply tube (not shown) that may or may not have a controllable
valve.
In an alternative embodiment shown in FIG. 17A, the electrically
conducting fluid is delivered from a fluid delivery element (not
shown) that is separate from catheter 460. In arthroscopic surgery,
for example, the body cavity will be flooded with isotonic saline
and the catheter 460 will be introduced into this flooded cavity.
Electrically conducting fluid will be continually resupplied to
maintain the conduction path between return electrode 624 and
electrode terminals 463.
FIG. 18 illustrates a method of removing tissue from a body lumen
within a patient's nose. As shown, the patient's nose includes a
nasal cavity 700 divided up by the inferior and middle nasal
conchas 702, 704, and a number of sinus cavities separated from the
nasal cavity by ethmoid bone 706. As shown, the frontal sinus 708
and the sphenoidal sinus 710 each include a passage or lumen 712,
714, respectively, extending through ethmoid bone 706 into the
nasal cavity 700. In addition, the sinus cavities have passages
(not shown) that connect each other. These passages often become
blocked with swollen or scarred tissue, which causes the sinus
cavities to fill, producing deep pain and pressure. Postnasal or
nasal drainage, nasal congestion with pressure, headaches, sinus
infections and nasal polyps are most commonly associated with
chronic sinusitis. Note that only the frontal sinus 305 and the
sphenoidal sinus 307 are shown in FIG. 18, but the procedure is
also applicable to the ethmoidal and maxillary sinuses. The ostium
720 for the maxillary sinus is shown in FIG. 18.
As shown in FIG. 18, the ablation region 464 of catheter 460 is
advanced through the nostril 722 into the nasal cavity 700 and to
the passage 712 leading to the frontal sinus 708. The catheter 460
may be advanced with a variety of techniques, such as a guidewire,
steerable catheter and the like. Once the surgeon has reached the
point of major blockage within passage 712, electrically conductive
fluid is delivered through one or more internal lumen(s) (not
shown) within the catheter to the tissue. Alternatively, the nasal
cavity 700 is filled with electrically conductive fluid (similar to
an arthroscopic procedure). In some embodiments, the catheter may
be configured to operate with a naturally occurring body fluid,
e.g., blood, as the conductive medium. The fluid flows past the
return electrode 624 to the electrode terminals 463 at the distal
end of the catheter shaft. The rate of fluid flow is controlled
with a valve (not shown) such that the zone between the occlusion
and electrode terminal(s) 463 is constantly immersed in the fluid.
The power supply 28 is then turned on and adjusted such that a high
frequency voltage difference is applied between electrode terminals
462 and return electrode 624. The electrically conductive fluid
provides the conduction path (see current flux lines) between
electrode terminals 463 and the return electrode 624.
In the preferred embodiment, the high frequency voltage is
sufficient to convert the electically conductive fluid (not shown)
between the occlusive media and electrode terminal(s) 463 into an
ionized vapor layer or plasma. As a result of the applied voltage
difference between electrode terminal(s) 463 and the occlusive
media, charged particles in the plasma are accelerated towards the
occlusion to cause dissociation of the molecular bonds within
tissue structures, as discussed above. During the process, products
of ablation and excess electrically conductive fluid, and other
fluids (e.g., blood) may be aspirated from the target site to
facilitate the surgeon's view. During ablation of the tissue, the
residual heat generated by the current flux lines (typically less
than 150.degree. C.), will usually be sufficient to coagulate any
severed blood vessels at the site. If not, the surgeon may switch
the power supply 28 into the coagulation mode by lowering the
voltage to a level below the threshold for fluid vaporization, as
discussed above. This simultaneous hemostasis results in less
bleeding and facilitates the surgeon's ability to perform the
procedure. Once the blockage has been removed, aeration and
drainage are reestablished to allow the sinuses to heal and return
to their normal function.
FIG. 19 is a coronal section of a patient's head illustrating the
paranasal sinuses in more detail. As shown, the nasal septum 750
extends through the center of the nasal cavity 700 between the
right and left portions 752, 754 of the maxillary sinus. A series
of winding passages 765 connect the nasal cavity 700 with the
maxillary sinus portions 752, 754. These passages 765 can become
partially or completely blocked. The systems and methods of the
present invention allow the surgeon to advance a small catheter
into these passages and volumetrically remove the blockage in a
minimally invasive manner, i.e., without causing significant damage
to the surrounding cartilage, the nasal septum or the sinuses.
* * * * *